Motor-Driven Angle Grinder

ABSTRACT

A motor driven angle grinder is described and which includes an electric motor; a transmission coupled to the electric motor and which includes a motor shaft and a tool spindle; a crown wheel in the form of a hat is provided and which forms a recess that receives the tool spindle and a bearing, and wherein the crown wheel defines toothing which surrounds the recess, and wherein the transmission housing and the angle grinder have low relative height profiles which permits the angle grinder to be used in restricted or tight space working environments.

The invention relates to a motor-driven angle grinder, in particular driven by an electric motor, having a motor housing accommodating the motor components and a transmission housing accommodating transmission components, having a motor shaft and a tool spindle which are oriented at an angle to one another via an angular gear arrangement having a crown wheel, wherein a grinding or separating tool which can be driven in rotation is mountable on the tool spindle.

A number of such angle grinders have been disclosed, in particular EP 1 938 924 A1.

It is the object of the present invention to improve an angle grinder of the mentioned type such that poorly accessible regions which are bordered in particular by sections at an acute angle to one another can be machined in an improved manner or can be machined in the first place.

In the case of an angle grinder of the mentioned type, this object is achieved according to the invention in that the crown wheel is formed in the shape of a hat and is arranged such that a recess forming the hat shape is oriented toward that side of the crown wheel that faces the tool and a toothing on the crown wheel is arranged radially outside an elevation, bordering the recess, of the crown wheel, on that side of the crown wheel that is remote from the tool, and in that the recess is dimensioned such that the tool spindle and a bearing device mounting the tool spindle with respect to a flange of the transmission housing extend in the axial direction into the recess.

On account of this configuration according to the invention, a flat construction, which has not hitherto been realized in the case of angle grinders, is achieved in the region of the transmission housing, and as a result, the range of application of the angle grinder is widened considerably even under spatially restricted conditions. As a result of the claimed configuration and orientation of the crown wheel, the bearing device for the tool spindle, which is typically a roller bearing device, is arranged at the level of the crown wheel within the transmission housing, thereby saving considerable axial installation space. However, this means that an elevation bordering the recess toward the other side is provided on the crown wheel. On account of the fact that the toothing of the crown wheel is, however, arranged radially outside this elevation, a drive component meshing with the crown wheel, for example a pinion driven by the motor shaft or fitted on the motor shaft, can also be arranged at least partially within the axial installation space of the crown wheel. As a result of this, too, optimal use is made of the available axial installation space and a minimum height of the transmission housing in the region of the tool spindle can be realized.

In a development of the invention, it is proposed that an in particular concentric portion of the flange of the transmission housing also extends in the axial direction into the recess in the crown wheel. In this way, the portion of the flange extending into the recess can form an accommodating region for the bearing device.

In further continuation of this concept of the invention, the bearing device is secured axially against falling out with respect to the flange of the transmission housing, in particular with respect to the concentric portion of the flange of the transmission housing, by an axially acting securing element, in particular a snap ring, wherein the axial securing element is fitted in a position engaging behind the flange.

In a preferred embodiment of the angle grinder according to the invention, a height of the transmission housing in the region of the grinding or separating tool is at most 40 mm, particularly at most 38 mm, particularly at most 36 mm, particularly at most 34 mm and further particularly at most 32 mm, said height being measured in the axial direction of the tool spindle from an outer side, that faces the tool, as far as a top side, that is remote from the tool, of the transmission housing. It proves to be advantageous in this case for the transmission housing to have this maximum height over the entire extent of the grinding or separating tool. However, the transmission housing should at least have this maximum height as far as the longitudinal axis of the tool spindle.

Since angle grinders having such a low height of the transmission housing in the region of the tool spindle have not hitherto been realized, protection is of course claimed for this concept of the invention. In particular, protection is claimed for this concept of the invention in conjunction with the proposal that the crown wheel is formed in the shape of a hat and is arranged such that a recess forming the hat shape is oriented toward that side of the crown wheel that faces the tool.

According to a further embodiment of the angle grinder according to the invention, the transmission housing is beveled toward the front and preferably toward the sides on that side of a longitudinal axis of the tool spindle that is remote from the motor housing, such that the extended course of the bevel does not project beyond a peripheral edge of the tool. In known angle grinders, the extended course of the bevel intersects the plane of the tool clearly outside and in front of the peripheral edge of the tool. This severely restricts the usability of the machine tool at poorly accessible regions, as is shown in FIG. 1. Independent protection is claimed for this further concept of the invention, too.

In a development of this concept of the invention, a configuration is proposed, wherein a tangent to the transmission housing forms an angle with the plane of the tool at the peripheral edge of the tool of at most 42°, particularly of at most 40°, particularly of at most 38°, particularly of at most 37° and particularly of 35°. Single-handed protection is claimed for this feature, too.

It also proves to be advantageous for the tool spindle to be produced as a separate component from the crown wheel and to extend through the crown wheel and for a second bearing device for the tool spindle to be provided on that side of the crown wheel that is remote from the tool.

According to a further embodiment of the angle grinder according to the invention, it is proposed that the transmission housing is formed in an elongate manner such that a dimension of the transmission housing starting from a longitudinal axis of the tool spindle in the direction of the motor housing is greater than the radius of the tool, so that the tool does not engage beneath the motor housing. This elongate configuration of the transmission housing, which lengthens a typical long handle shape of the motor housing, makes it possible for the first time to arrange the tool with respect to the components of the transmission housing and of the motor housing such that it does not engage beneath the motor housing. However, this opens up the possibility of arranging the tool closer to the transmission housing in the direction of the longitudinal axis of the tool spindle, thereby again saving overall axial height of the transmission housing region. Independent protection is claimed for this concept of the invention, too, in particular in conjunction with the feature whereby the crown wheel is formed in the shape of a hat and is arranged such that a recess forming the hat shape is oriented toward that aide of the crown wheel that faces the tool.

In a further development of this concept of the invention, it is proposed for the tool to be arranged on the transmission housing in such a manner that the upper and/or lower tool plane of the tool, when the machine tool is viewed from the side and perpendicularly to the tool spindle, does not come to rest beneath the motor housing.

It also proves to be advantageous for the machine tool and in particular the transmission housing and the components thereof to be configured such that a protective hood for the tool also does not engage beneath the motor housing but, when the machine tool is viewed from the side perpendicularly to the tool spindle, is arranged next to the end of the motor housing, i.e. entirely within the region of the transmission housing. Specifically, on account of the low flat construction according to the invention of the transmission housing, it is possible to arrange the protective hood and a holder for the protective hood entirely beneath that side of the flange of the transmission housing that faces the tool, so that it axially overlaps the installation space of the motor housing but—as mentioned—is arranged in front of the motor housing. Also as a result, a flat construction, which has never been realized before, of the angle grinder as a whole can be realized, specifically measured from a lower tool plane to an upper side, that is remote from the tool, of the transmission housing.

Further features, details and advantages of the invention can be gathered from the appended patent claims and from the illustrations and the following description of a preferred embodiment of the invention. In the drawing:

FIG. 1 illustrates the restricted usability of a known angle grinder;

FIG. 2 illustrates the improved usability of an angle grinder according to the invention having a flat construction;

FIG. 3 shows a sectional view of an angle grinder according to the invention in the region of the transmission housing;

FIG. 4 and FIG. 5 show an exploded illustration of a number of components of the angle grinder in the region of the tool spindle.

FIGS. 1 and 2 show the usability of a known angle grinder 2 and an angle grinder 4 according to the invention having a flat construction. In the case of the angle grinder 2, a transmission housing 6 is very tall overall and the tool plane of the grinding or separating tool 8 is at a great distance from that side 10 of the transmission housing 6 that faces the tool. The tool 8 engages beneath a motor housing 12 which adjoins the transmission housing. On account of the large overall axial height, the usability of the known angle grinder 2 is restricted in poorly accessible regions, which are illustrated here by way of pipe sections that are oriented at an acute angle to one another. By contrast, the angle grinder 4 according to the invention according to FIG. 2 is very flat overall. The height of the transmission housing is heavily reduced compared with known embodiments. The grinding or separating tool 16 is located entirely beneath the transmission housing 14; it does not engage beneath the motor housing 18 as in known embodiments. Even a protective hood 20 is provided beneath the transmission housing 14 and thus likewise does not engage beneath the motor housing, as a result of which the overall flat construction can be reduced further. It can be seen from FIG. 2 that the usability of the angle grinder 4 according to the invention in regions of limited accessibility is considerably improved. According to FIG. 2, the transition region of the pipes can be reached and machined without problems, even when the transition region is bordered by an acute angle of only 35° between the components.

FIGS. 3-5 show the configuration of the drivetrain of the angle grinder 4 according to the invention, including an angular gear arrangement 22. Illustrated is a motor shaft 26, which is drive-connected if appropriate via a transmission arrangement, which is not illustrated in detail, to a pinion shaft 30 which is aligned with the motor shaft 26. At its front free end, the pinion shaft 30 carries a pinion wheel 32, which meshes with a crown wheel 34 and thus forms the angular gear arrangement 22. A tool spindle 36 is formed as a component separate from the crown wheel 34 and extends through the crown wheel 34 through a central shaft opening 38. A longitudinal axis 40 of the tool spindle 36 extends in this case at right angles to a longitudinal axis 42 of the pinion shaft 30 and defines an axial direction 43 of the tool spindle.

The tool spindle 36 further passes through a flange 44 of the transmission housing 14 in a manner which will be described in more detail, the flange 44 being configured in the form of a plate and the transmission housing 14 terminating toward the outside in the direction of the tool side. At a free end section 46, the tool spindle 36 carries for example an external thread 48, onto which there can be screwed a clamping means 50 which tightens the tool 16 against an axial abutment section 52 of the tool spindle 36 or against a tool abutment flange fitted on the tool spindle.

The angular gear arrangement 22 is configured in detail in the following manner:

The crown gear 34 is formed in the shape of a hat. It comprises a recess 54 which is open toward the tool side and is bordered by an elevation 56 formed toward the other side of the crown wheel 34. This elevation 56 is formed in a dome-shaped manner and can have, for example, a cylindrical or conical basic shape as viewed from the outside, although this is not absolutely necessary. Radially outside this elevation 56, the crown wheel 34 has a brim-like region 58 of the hat shape, said brim-like region 58 carrying a toothing 60 of the crown wheel 34 radially outside the elevation 56, on that side of the crown wheel 34 that is remote from the tool.

Thus, as can be seen from the figures and was mentioned above, the crown wheel 34 is oriented such that its recess 54 is open toward the side that faces the tool and such that its toothing 60 is formed on that side of the crown wheel 34 that is remote from the tool. In this way, the pinion shaft 30 and the pinion wheel 32 are provided at least partially within the axial installation space of the crown wheel 34, above its toothing 60, thereby reducing the overall axial height. It further proves to be advantageous for a bearing device 62 in the form of a roller bearing to be accommodated within the recess 54. The bearing device 62 is held within a concentric portion 64 of the flange 44 on the side thereof that is remote from the tool. This concentric portion 64 likewise projects axially into the recess 54 of the crown wheel 34 and in the process holds the bearing device 62, in particular an outer shell of a ball bearing. The bearing device 62 is secured axially against falling out by an axially acting securing element 66 in the form of a snap ring 68, which can be clipped into an inner circumferential groove 70 in the wall of the concentric portion 64.

As mentioned, the tool spindle 36 extends through the central shaft opening 38 in the crown wheel 34 and projects axially beyond an outer side 74 of the elevation 56 by way of an end section 72 that is remote from the tool. Provided there is a second bearing device 76, which mounts the tool spindle 36 against the transmission housing 14. This bearing point is closed from above by a bearing cover 78 (only FIG. 3).

The components illustrated in FIGS. 4 and 5 of the drivetrain are advantageously configured as a premountable subassembly. This subassembly can be mounted by way of example by mounting the flange 44 on the underside of the transmission housing 14 by means of screw connections. As a result, the transmission housing 14 is also closed off in a dustproof manner toward the outside. The bearing devices 62 and 76 in this case also assume a sealing function.

The extremely flat construction of the transmission housing 14 and of the angle grinder 4 overall can be seen from the figures. A dimension H from a lower side, that faces the tool, of the transmission housing 14, or the flange thereof 44, to a top side of the transmission housing 6 in the entire region above the tool 16 is advantageously only about 36 mm; at the point of the longitudinal axis 40 of the tool spindle 36 it is only about 34.5 mm.

A tangent 82 to the transmission housing 14, in a longitudinal center plane of the angle grinder, said tangent at the same time touching a peripheral edge 84 of the tool 16, forms an angle of only about 35° with the tool plane 86 in the exemplary and preferably illustrated case. This also considerably improves the accessibility of acute-angle regions when the angle grinder 4 according to the invention is used.

The initially mentioned protective hood 20 can be removed from the angle grinder and attached thereto again without tools and can be locked in various rotational positions. The attachment and tool-less adjustment of the protective hood 20 is described in detail in DE 10 2008 059 249.8 by the applicant, and so reference is made thereto in this regard. 

1. A motor-driven angle grinder comprising: an electric motor, enclosed within a motor housing; a transmission housing accommodating transmission components, and having a motor shaft coupled to the electric motor, and a tool spindle which are oriented at an angle to one another via an angular gear arrangement; a grinding or separating tool which can be driven in rotation and which is mounted on the tool spindle; a crown wheel forming a portion of the angular gear arrangement is formed in the shape of a hat, and further defines a recess and wherein the recess is arranged such that a recess forming the hat shape is oriented toward a side of the crown wheel that faces the tool and wherein the crown wheel further defines toothing and wherein the toothing on the crown wheel is arranged in a location which is radially outside an elevation which borders the recess, of the crown wheel, and which is located on a side of the crown wheel that is remote from the tool, and wherein the recess is dimensioned so as to receive the tool spindle and a bearing device which engages the tool spindle; and a flange forming a portion of the transmission housing extends in the axial direction and into the recess, and wherein the tool spindle is mounted relative to the flange by the bearing device.
 2. An angle grinder as claimed in claim 1, and wherein the flange has a concentric portion which extends in the axial direction and into the recess.
 3. An angle grinder as claimed in claim 2, and wherein the bearing device is secured axially against falling out of engagement relative to the flange and which forms a portion of the transmission housing, and in particular with respect to the concentric portion of the flange of the transmission housing, by an axially acting securing element which takes the form of a snap ring and wherein the securing element is fitted in a position which engages behind the flange.
 4. An angle grinder as claimed in claim 3, and wherein a height (H) of the transmission housing in the region of the grinding or separating tool lies in a range of about 32 to about 40 mm said height (H) being measured in the axial direction of the tool spindle from an outer side, that faces the tool, and as far as a top side, that is remote from the tool, of the transmission housing.
 5. An angle grinder as claimed in claim 4, and wherein the transmission housing is beveled toward a front of the transmission housing and preferably toward the sides, and on that side of a longitudinal axis of the tool spindle that is remote from the motor housing, such that the extended course of the bevel does not project beyond a peripheral edge of the tool.
 6. An angle grinder as claimed in claim 5, and wherein a tangent is formed relative to the transmission housing and which forms an angle with the plane of the tool at the peripheral edge of the tool and particularly of 35° and which lies in a range of about 35° to about 42°.
 7. An angle grinder as claimed in claim 6, and wherein the tool spindle extends through the crown wheel and a second bearing device for supporting the tool spindle is provided on that side of the crown wheel that is remote from the tool.
 8. An angle grinder as claimed in claim 7, and wherein the transmission housing is formed in an elongate manner such that a dimension of the transmission housing starting from a longitudinal axis of the tool spindle in the direction of the motor housing is greater than the radius of the tool, so that the tool does not engage beneath the motor housing.
 9. An angle grinder as claimed in claim 8, and wherein an upper and/or lower tool plane of the tool, when the machine tool is viewed from one side and perpendicularly relative to the tool spindle, does not come to rest beneath the motor housing.
 10. An angle grinder as claimed in claim 9, and wherein a protective hood for the tool also does not engage beneath the motor housing. 